C# - Foreign key references invalid table - Basic

问题:

Trying to make my first project in C#. However, it's very frustrating so far. This is a problem I can't solve, since I don't see anything wrong.

I'm trying to just do a simple migrate in my DB.

Users migration file

 public override void Up()
        {
            CreateTable(
                "dbo.Users",
                c => new
                    {
                        user_id = c.Int(nullable: false, identity: true),
                        first_name = c.String(),
                        last_name = c.String(),
                        email = c.String(),
                        role = c.String(),
                    })
                .PrimaryKey(t => t.user_id);
        }

Locations migration file

 public override void Up()
        {
            CreateTable(
                "dbo.Locations",
                c => new
                {
                    loc_id = c.Int(nullable: false, identity: true),
                    loc_name = c.String(),
                })
            .PrimaryKey(t => t.loc_id);

            CreateTable(
                "dbo.UserLoc",
                c => new
                {
                    ul_id = c.Int(nullable: false, identity: true),
                    fk_user_id = c.Int(nullable: false),
                    fk_loc_id = c.Int(nullable: false),
                })
            .PrimaryKey(t => t.ul_id);
            AddForeignKey("dbo.UserLoc", "fk_user_id", "dbo.Users", "user_id");
            AddForeignKey("dbo.UserLoc", "fk_loc_id", "dbo.Locations", "loc_id");
        }

Models:

User.cs

public class User
{
    [Key]
    public int user_id { get; set; }

    public string firs_tname { get; set; }
    public string last_name { get; set; }
    public string email { get; set; }
    public string role { get; set; }
}

Location.cs

public class Locations
{
    [Key]
    public int loc_id { get; set; }
    public int loc_name { get; set; }
}

UserLoc.cs

public class UserLoc
{
    [Key]
    public int ul_id { get; set; }

    [ForeignKey("Users")]
    public int fk_user_id { get; set; }
    public virtual User user { get; set; }

    [ForeignKey("Locations")]
    public int fk_location_id { get; set; }
    public virtual Locations location { get; set; }
}

Every time I want to migrate I get the same error

Foreign key 'FK_dbo.UserLoc_dbo.Users_fk_user_id' references invalid table 'dbo.Users'. Could not create constraint or index. See previous errors.

What am I doing wrong?

回答1:

First I recommend you to change the FK name that you are using in the ForeignKey attributes for the navigation property names:

public class UserLoc
{
    [Key]
    public int ul_id { get; set; }

    [ForeignKey("user")]
    public int fk_user_id { get; set; }
    public virtual User user { get; set; }

    [ForeignKey("location")]
    public int fk_location_id { get; set; }
    public virtual Locations location { get; set; }
}

This way you are telling it which navigation property represents the relationship it is a foreign key for.

After that, remove the old migration and try to run again Add-Migration command to regenerate it. You should see now that CreateIndex method is called before AddForeignKey method:

CreateIndex("dbo.UserLoc", "fk_user_id");
AddForeignKey("dbo.UserLoc", "fk_user_id", "dbo.Users", "user_id");

CreateIndex("dbo.UserLoc", "fk_loc_id");
AddForeignKey("dbo.UserLoc", "fk_loc_id", "dbo.Locations", "loc_id");